lavf/tcp: check return value of setsockopt.

when setsockopt fail, use ff_log_net_error to dump the string
describing for error number.
Signed-off-by: Jun Zhao <mypopydev@gmail.com>

libavformat/tcp.c

@@ -151,17 +151,25 @@ static int tcp_open(URLContext *h, const char *uri, int flags)
     /* Set the socket's send or receive buffer sizes, if specified.
        If unspecified or setting fails, system default is used. */
     if (s->recv_buffer_size > 0) {
-        setsockopt (fd, SOL_SOCKET, SO_RCVBUF, &s->recv_buffer_size, sizeof (s->recv_buffer_size));
+        if (setsockopt (fd, SOL_SOCKET, SO_RCVBUF, &s->recv_buffer_size, sizeof (s->recv_buffer_size))) {
+            ff_log_net_error(h, AV_LOG_WARNING, "setsockopt(SO_RCVBUF)");
+        }
     }
     if (s->send_buffer_size > 0) {
-        setsockopt (fd, SOL_SOCKET, SO_SNDBUF, &s->send_buffer_size, sizeof (s->send_buffer_size));
+        if (setsockopt (fd, SOL_SOCKET, SO_SNDBUF, &s->send_buffer_size, sizeof (s->send_buffer_size))) {
+            ff_log_net_error(h, AV_LOG_WARNING, "setsockopt(SO_SNDBUF)");
+        }
     }
     if (s->tcp_nodelay > 0) {
-        setsockopt (fd, IPPROTO_TCP, TCP_NODELAY, &s->tcp_nodelay, sizeof (s->tcp_nodelay));
+        if (setsockopt (fd, IPPROTO_TCP, TCP_NODELAY, &s->tcp_nodelay, sizeof (s->tcp_nodelay))) {
+            ff_log_net_error(h, AV_LOG_WARNING, "setsockopt(TCP_NODELAY)");
+        }
     }
 #if !HAVE_WINSOCK2_H
     if (s->tcp_mss > 0) {
-        setsockopt (fd, IPPROTO_TCP, TCP_MAXSEG, &s->tcp_mss, sizeof (s->tcp_mss));
+        if (setsockopt (fd, IPPROTO_TCP, TCP_MAXSEG, &s->tcp_mss, sizeof (s->tcp_mss))) {
+            ff_log_net_error(h, AV_LOG_WARNING, "setsockopt(TCP_MAXSEG)");
+        }
     }
 #endif /* !HAVE_WINSOCK2_H */